A data transfer device that transfers data (e.g., a frame) received from one external device to another external device is known. A data transfer device described in Patent Document 1 as one of data transfer devices of this type is equipped with a communication establishment processor.
The communication establishment processor transfers and receives communication establishing information for establishing communication with an external device connected via a communication port, to and from the external device. Moreover the communication establishment processor transmits communication maintaining information for maintaining the establishment of communication with an external device to the external device every time a predetermined transmission period elapses.
Thus, communication between the data transfer device and the external device is established, and the establishment of the communication can be maintained.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. JP-A 2008-160227
There is a case that, in the data transfer device described above, an operation of the communication establishment processor must be stopped (e.g., when a firmware program is updated in a case that the communication establishment processor is configured by a CPU that executes the firmware program, or when failure occurs in the communication establishment processor).
In this case, the data transfer device cannot transmit communication maintaining information. Therefore, in such a case, there is a problem that it is impossible to maintain the establishment of communication with an external device.